- Where $URL is the URL of the file.
- Replace the $2 by $3 at the end to get a human-readable size.
Credits to svanberg @ ArchLinux forums for original idea.
Edit: Replaced command with better version by FRUiT. (removed unnecessary grep)

This command list and sort files by size and in reverse order, the reverse order is very helpful when you have a very long list and wish to have the biggest files at the bottom so you don't have scrool up.
The file size info is in human readable output, so ex. 1K..234M...3G
Tested with Linux (Red Hat Enterprise Edition)

This modifies the output of ls so that the file size has commas every three digits. It makes room for the commas by destructively eating any characters to the left of the size, which is probably okay since that's just the "group".
Note that I did not write this, I merely cleaned it up and shortened it with extended regular expressions. The original shell script, entitled "sl", came with this description:
: '
: For tired eyes (sigh), do an ls -lF plus whatever other flags you give
: but expand the file size with commas every 3 digits. Really helps me
: distinguish megabytes from hundreds of kbytes...
:
: Corey Satten, corey@cac.washington.edu, 11/8/89
: '
Of course, some may suggest that fancy new "human friendly" options, like "ls -Shrl", have made Corey's script obsolete. They are probably right. Yet, at times, still I find it handy. The new-fangled "human-readable" numbers can be annoying when I have to glance at the letter at the end to figure out what order of magnitude is even being talked about. (There's a big difference between 386M and 386P!). But with this nifty script, the number itself acts like a histogram, a quick visual indicator of "bigness" for tired eyes. :-)

This will create a 10 MB file named testfile.txt. Change the count parameter to change the size of the file.
As one commenter pointed out, yes /dev/random can be used, but the content doesn't matter if you just need a file of a specific size for testing purposes, which is why I used /dev/zero. The file size is what matters, not the content. It's 10 MB either way. "Random" just referred to "any file - content not specific"

The command gives size of all files smaller than 1024k, this information, together with disk usage, can help determin file system parameter (e.g. block size) or storage device (e.g. SSD v.s. HDD).
Note if you use awk instead of "cut| dc", you easily breach maximum allowed number of records in awk.

This one-liner is for cron jobs that need to provide some basic information about a filesystem and the time it takes to complete the operation. You can swap out the di command for df or du if that's your thing. The |& redirections the stderr and stdout to the mail command.
How to configure the variables.
TOFSCK=/path/to/mount
FSCKDEV=/dev/path/device
or
FSCKDEV=`grep $TOFSCK /proc/mounts | cut -f1 -d" "`
MAILSUB="weekly file system check $TOFSCK "